1. Field of the Invention
The present invention relates to an electromagnetic clutch, more particularly, to a method for manufacturing a rotor frame of an electromagnetic clutch that can be used in an automobile air conditioning system.
2. Description of the Prior Art
In Japanese Patent Application Publication No. 57-40126, a method for manufacturing a rotor frame of an electromagnetic clutch is disclosed. This method comprises forming a rotor frame by cold forging from a ring-shaped lump of iron. However, shaping an appropriately large ring of iron requires a large, expensive forging machine that can provide the required manufacturing pressures which are typically on the order of 1,500 to 2,000 tons. It would be desirable to have a manufacturing method that does not require high manufacturing loads and heavy equipment.